Near-infrared cameras are used in a variety of applications, typically associated with imaging in low-light conditions. These applications include night-time surveillance and traffic monitoring, both of which benefit from a wide field of view (FOV). In surveillance, the wide FOV makes it possible to monitor a large area with a single camera. In traffic monitoring, a vehicle may be equipped with one or more cameras that image surroundings of the vehicle to, e.g., avoid collisions when driving at night. In some applications, the scene is illuminated with one or more light-emitting diodes emitting near-infrared light. A camera sensitive to near-infrared light then images this illumination light as it is scattered off of objects in the scene.
Most conventional wide FOV lens systems include a large number of lens elements and lens surfaces, for example six lens elements with eleven lens surfaces/interfaces. This allows for incorporating, into a single lens system, many different materials having diverse indices of refraction so as to properly propagate wide-angle rays through the lens system. Typically, the lens (or lenses) closest to the scene has a very large diameter in order to collect and guide these wide-angle rays.